The rapidly approaching smart/wearable energy era necessitates advanced rechargeable power sources with reliable electrochemical properties and versatile form factors. Here, as a unique and promising energy storage system to address this issue, we demonstrate a new class of heterolayered, one-dimensional (1D) nanobuilding block mat (h-nanomat) battery based on unitized separator/electrode assembly (SEA) architecture. The unitized SEAs consist of wood cellulose nanofibril (CNF) separator membranes and metallic current collector-/polymeric binder-free electrodes comprising solely single-walled carbon nanotube (SWNT)-netted electrode active materials (LiFePO4 (cathode) and Li4Ti5O12 (anode) powders are chosen as model systems to explore the proof of concept for h-nanomat batteries). The nanoporous CNF separator plays a critical role in securing the tightly interlocked electrode-separator interface. The SWNTs in the SEAs exhibit multifunctional roles as electron conductive additives, binders, current collectors and also non-Faradaic active materials. This structural/physicochemical uniqueness of the SEAs allows significant improvements in the mass loading of electrode active materials, electron transport pathways, electrolyte accessibility and misalignment-proof of separator/electrode interface. As a result, the h-nanomat batteries, which are easily fabricated by stacking anode SEA and cathode SEA, provide unprecedented advances in the electrochemical performance, shape flexibility and safety tolerance far beyond those achievable with conventional battery technologies. We anticipate that the h-nanomat batteries will open 1D nanobuilding block-driven new architectural design/opportunity for development of next-generation energy storage systems.

Activated carbon is carbon produced from carbonaceous source materials, such as coconut shells, coals, and woods. In this study, an activated carbon production system was analyzed by carbonization and activation in terms of environmental impact and human health. The feedstock of wood wastes for the system reduced fossil fuel consumption and disposal costs. Life cycle assessment methodology was used to analyze the environmental impacts of the system, and the functional unit was one tonne of wood wastes. The boundary expansion method was applied to analyze the wood waste recycling process for activated carbon production. An environmental credit was quantified by avoided impact analysis. Specifically, greenhouse gases discharged from 1 kg of activated carbon production system by feeding wood wastes were evaluated. We found that this system reduced global warming potential of approximately 9.69E+00 kg CO2-eq. compared to the process using coals. The environmental benefits for activated carbon production from wood wastes were analyzed in contrast to other disposal methods. The results showed that the activated carbon system using one tonne of wood wastes has an environmental benefit of 163 kg CO2-eq. for reducing global warming potential in comparison with the same amount of wood wastes disposal by landfilling.

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Cellulose, which is one of the most-abundant and -renewable natural resources, has been extensively explored as an alternative substance for electrode materials such as activated carbons. Here, we demonstrate a new class of coffee-mediated green activation of cellulose as a new environmentally benign chemical-activation strategy and its potential use for all-paper flexible supercapacitors. A piece of paper towel is soaked in espresso coffee (acting as a natural activating agent) and then pyrolyzed to yield paper-derived activated carbons (denoted as "EK-ACs"). Potassium ions (K), a core ingredient of espresso, play a viable role in facilitating pyrolysis kinetics and also in achieving a well-developed microporous structure in the EK-ACs. As a result, the EK-ACs show significant improvement in specific capacitance (131 F g at a scan rate of 1.0 mV s) over control ACs (64 F g) obtained from the carbonization of a pristine paper towel. All-paper flexible supercapacitors are fabricated by assembling EK-ACs/carbon nanotube mixture-embedded paper towels (as electrodes), poly(vinyl alcohol)/KOH mixture-impregnated paper towels (as electrolytes), and polydimethylsiloxane-infiltrated paper towels (as packaging substances). The introduction of the EK-ACs (as an electrode material) and the paper towel (as a deformable and compliant substrate) enables the resulting all-paper supercapacitor to provide reliable and sustainable cell performance as well as exceptional mechanical flexibility. Notably, no appreciable loss in the cell capacitance is observed after repeated bending (over 5000 cycles) or multiple folding. The coffee-mediated green activation of cellulose and the resultant all-paper flexible supercapacitors open new material and system opportunities for eco-friendly high-performance flexible power sources.

The effect of carbonization temperature on the electromagnetic interference shielding effectiveness, electrical resistivity, and mechanical performance of medium density fiberboards carbonized in a vacuum furnace under a gas flow of nitrogen (200 mL/min) between 400℃ and 1500℃ was investigated. The medium density fiberboards specimens carbonized below 700℃ showed stable and low electromagnetic interference values (1.3–7.6 dB) between 10 MHz and 1 GHz frequency. The electromagnetic interference (average 43.1 dB) of the MDF specimens carbonized at 800℃ were suitable for industrial applications. However, the MDF specimens carbonized above 900–1500℃ showed high electromagnetic interference values (66.8–84.6 dB). When the carbonization temperature increased from 600℃ to 700℃, the electrical resistivity of the specimens greatly decreased (180.9 × 103 to 137.5 Ω-cm). A further increment in the carbonization temperature (1200℃) had a small effect on the electrical resistivity (5.8 Ω-cm) of the specimens and no effect between 1300℃ (0.5 Ω-cm) and 1500℃ (0.5 Ω-cm). The carbonized specimens showed lower modulus of rupture and internal bond strength values than the untreated specimens but the differences between the strength values of the untreated specimens and the carbonized specimens decreased with increasing carbonization temperature. The modulus of elasticities of the specimens carbonized above 800℃ were higher than the untreated specimens.